The long-term objectives of the project are the understanding of the biochemical properties of leukotriene C synthase and its possible role in airways diseases, as well as the development and assay of specific inhibitors of the enzyme. Leukotriene C synthase will be purified from the particulate fraction of mouse mastocytoma cells in the first phase of the investigation. Later, the enzyme will be isolated from other sources known to produce leukotriene C, such as rat basophilic leukemia cells and human lung tissue. The purified leukotriene C synthase will be characterized in detail and compared with previously studied glutathione transferases from mouse, rat and human tissues. Mechanisms of biological control of the synthase will be considered. Particular attention will be given to the kinetic properties and distinctive inhibition characteristics of leukotriene C synthase in view of the long-term goal of preventing symptoms of asthma by way of inactivating the enzyme. Active-site-directed inhibitors, in particular suicide substrates, will be designed and tested. Antibodies, both polyclonal and monoclonal, will be raised against the enzyme and used for studies of the distributions of the enzyme in different tissues and subcellular compartments. Leukotriene A and C biosynthesis will be measured in cells and secretions from human airways, and possible differences between normal individuals and patients with airways diseases will be defined. Nasal and bronchial lavage will be used for measurements of leukotriene levels, whereas nasal abrasio will be used as the primary source of cells for assay of enzyme activities. Patients with obstructive bronchitis, asthma, and allergic rhinitis are primary target groups. One aim of the study is to establish the role of leukotrienes in the expression of these diseases. Another aim, of clinical and diagnostic potential, is to what extent changes in leukotriene synthesis can be used for classification of infants with obstructive bronchitis. The aim is to find a method of identifying patients who will eventually develop asthma. Further, the clinical effects of pharmacotherapy of children, with obstructive bronchitis showing the same symptoms, are unpredictable. The three types of drugs commonly used are: (1) epinephrine (-adrenergic receptor agonist), (2) terbutaline (2-adrenergic receptor agonist), and (3) theophyllamine (phosphodiesterase inhibitor). A third goal is therefore to establish if a state of altered leukotriene metabolism can form a basis for selecting a proper pharmacotherapy.